In recent years, with the wide-spread use of items employing the Near Field Communication (NFC) technology such as the RFID (Radio Frequency IDentification) system and noncontact IC cards, devices using a coil as an antenna are widely used. A known example of such a device is a wireless (noncontact) charging device employing the electromagnetic induction phenomenon. In this wireless charging device, a receiving antenna (secondary coil) is placed so as to face a transmitting antenna (primary coil), and a magnetic flux generated by passing a current through the transmitting antenna is used to generate a current in the receiving antenna. Such antennas are becoming common as charging devices for mobile devices (for example, refer to Japanese Unexamined Patent Application Publication No. 11-266545).